1. Field of the Invention
The present invention relates generally to archery bows and more particularly pertains to an improved compression molded archery bow limb for use in a compound bow and method for manufacturing the same.
2. Description of the Prior Art
Archery bow limbs perform the important function of storing energy when the archer draws the bowstring. When the bowstring is drawn, the pre-stressed bow limbs, which are typically made of resilient material, are further flexed to store additional energy. When the bowstring is released, the stored energy propels the arrow.
In conventional compound bows, the limb is typically formed of a single element of rectangular cross section, wherein one end is attached to the bow handle and the other end has a limb tip slot formed therein, in which an eccentric wheel is mounted.
Reinforced glass fiber materials have been utilized in archery bow limbs for a number of years. In some instances, the limb profile is machined from extruded solid glass fiber billets, and in other instances the limb profile is machined from pre-formed compression molded billets, which in some cases may be pre-formed to such near net shape that only secondary machining operations are required to remove excess material from the limb tip area and from the butt slot area, where the limb is joined to the handle. In all such cases, the secondary machining operations are costly and time consuming. Further, the machining operations result in the severing of load bearing fibers which reduces the maximum limb operating stress level and the fatigue life of the limbs.
To lessen the problems associated with machining the reinforced glass fiber material, several processes have been developed, such as those disclosed in U.S. Pat. Nos. 4,649,889; 4,660,537; and 4,735,667. More recently, there is disclosed in U.S. Pat. No. 5,141,689, issued to G. Simonds, a method of forming a partial limb tip slot in a molded limb profile, and then severing the remaining glass fibers in the limb tip slot area to form the limb tip. This method reduces the number of glass fibers that are severed so that the fatigue life of the resultant limb tip is substantially improved, and the necessity of providing reinforcement washers to the limb tip slot is avoided. It is not believed, however, that a glass fiber limb for a compound bow has been produced which completely avoided having to sever glass fiber filaments when the limb tip slot was formed.
Further, it was popularly believed (see, for example, U.S. Pat. No. 4,735,667, issued to R. Johnson) that glass fiber limbs should be of a substantially constant cross sectional area in order to maintain a constant glass fiber to resin ratio in the limb.
Thus far the discussion has been concerned with conventional compound bows formed with single element glass fiber limbs of rectangular cross section. A different approach is disclosed in U.S. Pat. No. 4,350,138, issued to J. Caldwell. The limb portions disclosed therein are formed of left and right limb portions. Significantly, the limb portions disclosed therein are not compression molded, and it is not believed that any such split limb portions have been formed by compression molding despite the fact that the compression molding of limbs has been widely known for many years. More contemporaneous versions of such split limbs are, for example, being sold by Hoyt U.S.A. under the Alpha Tec mark and by High Country under the Split Force mark.